1. Field of the Invention
The present invention relates to a detergent composition containing a phosphorus-containing alkali metal (sodium or potassium) aluminosilicate as a builder.
2. Description of the Prior Art
Recently, attempts have been made to reduce the amount of sodium tripolyphosphate, which is a main detergent builder, incorporated in detergents because of the increased demand and reduced supply of sodium tripolyphosphate and because of the concern about eutrophication of lakes and rivers. Various substitutes for sodium tripolyphosphate have been developed and proposed.
Among the previously proposed substitute builders, water-insoluble aluminosilicates (called "zeolites") are now considered as being the most important. Water-insoluble aluminosilicates have been known as detergent builders for a long time, and they are disclosed in, for example, U.S. Pat. No. 1,419,625, British Pat. No. 339 355, British Pat. No. 462 591, U.S. Pat. No. 2,213,641 and British Pat. No. 522 097. These zeolites have recently been reconsidered, and various zeolite builders have been proposed in, for example, Japanese Patent Kokai No. 12381/75, Japanese Patent Kokai No. 21009/75, Japanese Patent Kokai No. 53404/75, Japanese Patent Kokai No. 37104/76 and West Germany Patent Application Laid-Open Specification No. 2 538 679. Most of these aluminosilicates are alkali metal or alkaline earth metal aluminosilicates represented by the following formula (A): EQU [x'(M'.sub.2 O or M"O).Al.sub.2 O.sub.3.y'(SiO.sub.2).w'(H.sub.2 O)](A)
wherein M' stands for an alkali metal, M" stands for an alkaline earth metal, and x',y' and w' are numbers showing the mole numbers of the respective components. x' and y' generally satisfy the following requirements: EQU 0.7.ltoreq.x'.ltoreq.1.5, and EQU 0.8.ltoreq.y'.ltoreq.6,
although these values are sometimes different in various proposals. w' is an optional positive number.
Specific examples of the previously proposed zeolite builders of this type include Molecular Sieve 3A ((Na.sub.2 O,K.sub.2 O).Al.sub.2 O.sub.3.2.00(SiO.sub.2).4.5(H.sub.2 O)), Molecular Sieve 4A ((Na.sub.2 O).Al.sub.2 O.sub.3.2.00(SiO.sub.2).4.5(H.sub.2 O)) and Molecular Sieve 13X ((Na.sub.2 O).Al.sub.2 O.sub.3.2.46(SiO.sub.2).6.4(H.sub.2 O)).
We have found that these previously proposed aluminosilicates, represented by the formula (A), have a relatively high calcium ion exchange capacity, but they are defective in that the magnesium ion exchange capacity is relatively low. As is well-known in the art, washing water (ordinary tap water) contains a large quantity of magnesium ions together with calcium ions, and these ions inhibit the washing action. As a result of our various investigations, it was found that in order to be suitable for effective use as a builder substitute for sodium tripolyphosphate, an aluminosilicate should have not only an appropriate calcium ion exchange capacity, but also an appropriate magnesium ion exchange capacity.